This invention relates to emergency evacuation equipment for aircraft, in particular, to inflatable aircraft evacuation slides.
The requirement for reliably evacuating airline passengers in the event of an emergency is well known. Emergencies at take-off and landing often demand swift removal of the passengers from the aircraft because of the potential for injuries from fire, explosion, or sinking in water. A conventional method of quickly evacuating a large number of passengers from an aircraft is to provide multiple emergency exits, each of which is equipped with an inflatable evacuation slide. Although evacuation slides permit passengers to quickly and safely descend from the level of the aircraft exit door to the ground, some passengers may experience difficulty moving from the seated position on the slide to a standing position exiting the slide. In an emergency situation, a passenger that is slow to exit the foot end of the slide may be struck by the next passenger descending the slide. Traditionally, the need to move passengers quickly away from the foot end of the evacuation slide has been accommodated by positioning a flight attendant at the foot end of the slide to assist the disembarking passengers. However, in an emergency, there may not be sufficient flight attendants to staff the foot end of each evacuation slide. For this reason, it would be advantageous if the foot end of an inflatable evacuation slide were designed so as to assist (e.g. by bouncing) the passenger upward onto his or her feet at the bottom xe2x80x9cfootxe2x80x9d end of the slide.
Prior art inflatable evacuation slides typically comprise several parallel tubular members attached together to form the sliding surface of the evacuation slide. Such slide construction is disclosed, for example, in U.S. Pat. No. 3,669,217 to Fisher and U.S. Pat. No. 4,434,870, also to Fisher. Use of multiple parallel tubes creates a rigid sliding surface, but at the cost of substantial weight devoted to the multiple tubes and, in any event, many such slides still do not provide sufficient springiness at the foot end to assist passengers to their feet. The requirement that aircraft evacuation slides be made lighter and lighter in weight has lead to the current generation aircraft evacuation slides which comprise a pair of inflatable tubular side rail members with a fabric sliding surface stretched therebetween. A head end and a toe end transverse tube maintain the side rails in a spaced-apart configuration while a plurality of lower truss members in combination with one or more straps provide the needed rigidity for the lightweight design.
The demand for lighter and lighter weight aircraft evacuation slides is being addressed by designing evacuation slides to operate a higher and higher pressures. A high pressure inflatable tubular structural member can be made smaller in cross section, thereby using less weight in fabric, while maintaining the same rigidity as a larger lower pressure structure. Therefore, while current state of the art aircraft evacuation slides typically operate at pressures of two to two and one-half pounds per square inch gauge (PSIG), one can expect to see aircraft evacuation slides operating at pressure ranges of 4 PSIG or even more in the near future. Unfortunately, although a small diameter high pressure tubular structural member has an equal resistance to deflection under load as a larger lower pressure inflatable tubular structural member, the high pressure tubular member has a substantially greater effective spring rate when subjected to a compressive load. Accordingly, what is needed is a high pressure evacuation slide having sufficient flexibility and springiness at the foot end to adequately catapult a sliding passenger onto his or her feet.
The present invention comprises an inflatable evacuation slide having a feature for propelling disembarking passengers onto their feet at the toe end of the slide. In one embodiment, the slide comprises a fabric sliding surface stretched between two lateral side rail tubes. The lateral side rail tubes are supported by plurality of transverse tubes and transverse trusses such that the side rail tubes maintain the sliding surface in a taut condition suitable for use as a slide. The foot end of the tube includes a, transverse tube having a reduced diameter and a lower surface that is suspended above the ground or other surface on which the foot end of the evacuation slide is resting. The suspended toe end transverse tube has a lower spring rate than a full-diameter transverse toe end tube. Therefore, the suspended toe end transverse tube provides the appropriate springiness for catapulting a sliding passenger onto his or her feet at the foot end of the slide notwithstanding the higher inflation pressure.